22 December 2013

I should be happy that Marmorkrebs is getting attention in national media, namely Time magazine. Instead, my reaction is more like:

The annoyance starts with the title:

“Critters So Ugly They Have to Mate With Themselves”

It’s not the critters that are ugly, it’s the title. Time used to have a little more dignity, but this sounds like it came from Buzzfeed. How demeaning to call these animals “ugly,” especially when the list contains not just the pretty marbled crayfish, but the handsome Komodo dragon (which doesn’t always reproduce asexually, putting like to the “have to” portion of the title), the sleek whiptail lizard, and the amazing looking hammerhead shark (which, again, doesn’t always reproduce asexually). “Mate with themselves” suggests self-fertilization, which some animals do, but these are all cases of parthenogenesis rather than self-fertilization

The subtitle isn’t better.

Immaculate conception may be something special among humans, but in the animal kingdom, it's always been part of the mix

Science and religion are often depicted as being at war, but they are united in the desire for good fact checking. The immaculate conception is not about the virgin birth of Jesus Christ. It’s about the conception of the Jesus’s mother, Mary, free of original sin.

I made a mistake with one guy on a radio station in Seattle. I said I
don’t think anyone really believes in the virgin birth and he said ‘I
do.’ I said ‘you don’t really’ and he said, ‘I do, I believe absolutely
in the immaculate conception.’ I told him he’d got it wrong and he said
‘What do you mean I’ve got it wrong? I’ve been a Catholic all my
life.’ The immaculate conception and the virgin birth are two different
concepts. He didn’t get this, but he believed in both.

The article manages to squeeze in three alternate spellings for Marmorkrebs in an equal number of paragraphs: “marmorkrebs,” and “Marmokrebs” (sic), both in a capitalized version (preferred here on the blog, following the German practice of capitalizing all nouns) and not.

And to add insult, the article is illustrated with this:

It’s not even a picture of the right species! It’s Procambarus clarkii, the common Louisiana red swamp crayfish! There are no shortage of Marmorkrebs pictures for use on this website and elsewhere. Time, you could have emailed me.

On the plus side, article does a nice job of linking to full text of the original scientific articles. And the actual text of the article, though short, is otherwise accurate.

18 December 2013

Christmas is the best time of the year to tell people about parthenogenesis, seeing that a story of human parthenogenesis forms a large part of Christmas tradition.

The British Medical Journal (or BMJ) has a new paper out that looks closely at reports of parthenogenesis in humans. According to Herring and colleagues, of over 7,000 young women (about 12-18) surveyed, about 0.8% of women reported pregnancy before they reported having sex.

As far as I can tell, they did not ask the women outright if they believed they got pregnant without the help of a man. They just extrapolated from whether women reported having had sex, whether they reported being pregnant, and comparing the dates. However, it seems likely that the women might have claimed virgin birth, given this interesting fact:

The virgins who reported pregnancies were more likely to have pledged chastity (30.5%) than the non-virgins who reported pregnancies (15.0%, P=0.01) or the other virgins (21.2%, P=0.007).

Also of note:

The virgins who reported pregnancy... were less likely to know how to use condoms than the non-virgins who reported pregnancy (79.6%, P=0.002).

The discussion mentions another fascinating group: the “born again virgins,” who reported having had sex early in the study, but reported themselves as virgins when surveyed again. This is actually much more common than virgin birth, accounting for about 3% of the women surveyed. This might be almost as miraculous as virgin birth.

I think there may be a few issues with self-reporting in this data set.

In addition to the interesting data, this paper also gets high points from me for referencing a Doctor Who episode in the introduction.

11 December 2013

The scientific name for Marmorkrebs continues to pose problems. First, the problem was that it didn’t have one. Then, Martin and colleagues (2010) proposed Procambarus fallax f. virginalis. The good news is that this name has been adopted by the scientific community. The bad news is that people are shortening it.

Because I am interested in the biology of both the sexual slough crayfish and the asexual Marmorkrebs, I have Google Scholar alerts set up for both. Recently, Google Scholar sent me a new “Procambarus fallax” alert for a new paper in Ecology and Evolution. The species appear in Table 1 and in the supplemental material.

I saw that the crayfish in the paper were bought in a pet store in the Netherlands, which made me wonder. The asexual Marmorkrebs are reportedly common in the European pet trade, but it was possible that this was the sexual form.

I emailed the authors, and co-author Menno Soes replied:

The examined specimen was the asexual form. In Dutch we call it marmerkreeft. I’ve never noticed the sexual form in Dutch pet shops.

Because this paper was about species living with crayfish, this distinction between slough crayfish and Marmorkrebs could change the interpretation slightly. If it was the sexual form, slough crayfish, it was conceivable that it was caught in the wild in Florida and shipped to Europe. If it was the asexual form, Marmorkrebs, this would be much less likely.

This isn’t the first time this has happened, either. Gallardo and Aldridge (2013) also used the species name Procambarus fallax alone, which significantly affects the interpretation of their results.

The moral of the story is: Authors and editors, please make sure to use the full species name for Marmorkrebs, Procambarus fallax f. virginalis, every time!

10 December 2013

Zieger E, Bräunig P, Harzsch S. 2013. A developmental study of serotonin-immunoreactive neurons in the embryonic brain of the marbled crayfish and the migratory locust: evidence for a homologous protocerebral group of neurons. Arthropod Structure & Development42(6): 507-520. http://dx.doi.org/10.1016/j.asd.2013.08.004

Abstract

It is well established that the brains of adult malacostracan crustaceans and winged insects display distinct homologies down to the level of single neuropils such as the central complex and the optic neuropils. We wanted to know if developing insect and crustacean brains also share similarities and therefore have explored how neurotransmitter systems arise during arthropod embryogenesis. Previously, Sintoni et al. (2007) had already reported a homology of an individually identified cluster of neurons in the embryonic crayfish and insect brain, the secondary head spot cells that express the Engrailed protein. In the present study, we have documented the ontogeny of the serotonergic system in embryonic brains of the Marbled Crayfish in comparison to Migratory Locust embryos using immunohistochemical methods combined with confocal laser-scan microscopy. In both species, we found a cluster of early emerging serotonin-immunoreactive neurons in the protocerebrum with neurites that cross to the contralateral brain hemisphere in a characteristic commissure suggesting a homology of this cell cluster. Our study is a first step towards a phylogenetic analysis of neurotransmitter system development and shows that, as for the ventral nerve cord, traits related to neurogenesis in the brain can provide valuable hints for resolving the much debated question of arthropod phylogeny.